From the assessment of the recovery capability of pseudomonas
fluorescens atcc 13525t after exposure to several glutaraldehyde (gta)
concentrations (100, 200 and 400 mg/l) and exposure times (1 and 2
hours), it was found that, for gta concentrations above 100 mg/l,
whatever the exposure time, bacterial cells presented different
growth patterns in solid media. after this statement, the recovered
cells were initially characterized using api ne20 strips and species
identification was obtained using the api database. the type culture
and the cells obtained after treatment with concentrations below
200 mg/l were identified as p. fluorescens. conversely, the identification
of cells exposed to higher concentrations of gta failed. the
electrophoretic profiles of both the type culture and the cells
exposed to gta were obtained by pcr, using the primer t3b. the
results showed identical profiles for the type culture and the cells
exposed to low gta concentrations, and a totally different pattern for
cells exposed to gta concentrations above 200 mg/l. sequencing of
the 16s rdna gene is under way in order to further clarify the
differences observed. the p. fluorescens atcc 13525 (used as control)
and the cells treated with 200 mg/l of gta during 2 hours were
selected for further studies. a comparative study was carried out
between the above referred cells in terms of morphological
structure, surface properties, respiratory activity, biofilm formation ability and susceptibility to gta. the results showed that the cells
treated with 200 mg/l of gta presented an elongated structure, were
about 30 times less active in terms of respiratory activity and were
more hydrophilic. concerning biofilm formation, both tested cells
presented biofilm formation ability, but the gta treated cells
produced about 2 times more mass of biofilm. however, this
biofilm had a specific respiratory activity 3 times less than the one
formed by the control culture. the biofilm behaviour immediately
after exposure to 200 mg/l of gta during 2 hours, was similar for
both situations studied, since a low biofilm removal and inactivation
was achieved. however, 7 hours after gta exposure, only 55% of the
biofilm formed by the control culture remained attached to the
surface, while for the biofilms formed by the treated cells all the
deposit remained attached to the surface.
the results obtained in this work indicate that cells submitted to gta
treatment may give rise to biofilms harder to remove and consequently
more persistent, than non-treated cells. therefore, care must
be taken in the selection and application of biocides in industrial
biofilms.